It is well known to those skilled in the art that overbraking and ensuing wheel lockup and wheel sliding on lightly loaded rapid and/or mass transit vehicles must be avoided since flat spots and damage to the wheels may occur during the braking of passenger trains. On heavily loaded railway vehicles there is the possibility that underbraking conditions may result in longer braking distances which may cause a railway train to overrun its normal stopping point at a station or a block section. In order to avoid an overbraking and underbraking condition, it is common practice to employ a standard variable load control valve device such as shown and disclosed in U.S. Pat. Nos. 3,460,872; 3,504,698; 3,517,971; 3,583,772, and 4,453,779. However, these previous variable load control valves which are used in existing brake equipment generally consist of a stepped or graduated piston to obtain brake cylinder pressure in proportion to the air spring pressure which corresponds to the load on the railway vehicle. The piston member includes dynamic 0-ring seals that move within a cylindrical bushing which is properly dimensioned to prevent air leakage between the air spring pressure chamber and brake cylinder pressure chamber. However, it has been found that the break-away friction characteristics associated with the dynamic 0-ring seals can cause a relatively large variation in the output pressure particularly when the valve has been idle or unoperated for a long period of time, such as, an overnight layover. Even though the 0-rings are thoroughly lubricated during the initial assembly of the valve, the lubricant is eventually dissipated or dispersed during the subsequent operation of the valve so that the amount of static friction is dramatically increased. Further, it will be appreciated that the brake cutoff pressure is a function of the ratio of the effective pressures that are supplied to the upper and lower surface areas of the graduated piston of the variable load control valve. Since various transit properties have different brake and load characteristics, it is necessary to provide a multitude of different pressure ratios between the air spring pressure and the brake cylinder pressure. However, in any given stepped piston type of variable load control valve, the pressure ratio is fixed and can only be varied or changed by substituting a different size of graduated piston, O-rings and bushings and, in some cases, a different intermediate filling member or casing to accommodate the different-size bushings. Thus, it will be appreciated that a relatively large number of different parts must be kept in inventory to ensure that the variable load valve devices are capable of being adapted to fill the braking requirements of the various transit authorities. Further, it will be noted that the close manufacturing and machining tolerances required by the different stepped pistons and the cooperatively associated bushings are expensive to machine and manufacture.